1. Field of the Invention
The present invention relates to an apparatus and method for molding electrical insulation about a cable in a nitrogen atmosphere and in one particular embodiment to an apparatus and method for molding insulation on a portion of an electrical cable or the like where the molded portion is qualitatively as good as adjacent portions of the cable. The molding operation may occur in a repair of a cable or a splice.
2. Description of the Prior Art
As disclosed in the above-mentioned patent applications, high voltage electrical cable generally comprises a central electrically conductive core, covered by a semi-conductive layer which in turn is covered by a layer of insulation. About this insulation is another semi-conductive layer covered by a conductive layer all of which in turn is covered by an outer jacket of insulative material. Most high voltage cables use cross-linked polyethylene as the insulative material.
Problems have occurred when portions of the cable are damaged, or when it is desired to splice. For example, realizing that electrical cable is manufactured in long strands, it can be readily appreciated that during the manufacturing process damage occurring anywhere on the cable damages the entire cable. If a burn hole appears in a long length of cable, the entire cable is defective, since it will have little or no realiability. A manufacturer of such a damaged cable can cut the cable, extract the damaged part and then attempt to sell the shorter lengths of cable individually; or the manufacturer could completely scrap the cable, that is, salvage reclaimable portions and begin the manufacturing process anew; or the manufacturer may attempt to repair the cable.
Without the proper pressurization, repairing or splicing a cable with cross-linked polyethylene provided a reliably poor cable. That is, unless the polyethylene is subjected to a substantial superatmospheric pressure while it cures, air pockets or voids or other irregularities appear which can cause the development of a corona which in time would lead to a failure of the cable.
The cable manufacturing industry has long sought ways in which to reliably repair a newly manufactured cable. Of course, it is understood that to be commercially feasible, any repair apparatus or method invented must function at a reasonable cost level. The cable using industry faces a similar problem in attempting to reliably field splice a cross-linked polyethylene cable. Once again any discontinuities formed would mean a rapid cable failure. Commercialization would also require a reliable apparatus at a reasonably low cost.